The present invention relates to a device by means of which to apply strips of material to packets of substantially parallelepiped shape.
In particular, the invention relates to a device for attaching a gummed strip across one edge of a cigarette packet, and more exactly, transversely to the longitudinal dimension of the packet, so as to adhere partly to one side face and partly to the adjacent front face.
The cigarette packets with which the present invention is concerned are those of flip-top type embodiment, including a box and a lid associated one with the other by way of a hinge fold.
In the event that the strip performs the function of a seal, it is laid over the edge interface between the lid and the box, in such a way that the lid cannot be raised unless the strip is torn through.
EP-34 790 discloses a device for applying strips of material to cigarette packets after the fashion outlined above, i.e. across one edge, in which the station where the strips are affixed is supplied with packets accommodated by the radial pockets of an indexing wheel.
The strips are supplied to the station by means of a vacuum roller disposed substantially tangential to the indexing wheel in such a way that upon arrival of each pocket at a selected location, a previously gummed strip is attached, transversely disposed, to the flank or side face of the corresponding packet. This accomplished, a given portion of the strip is left projecting beyond the longitudinal edge of the packet, ready to be folded over and flattened down against the adjacent face.
The operation is completed at a subsequent pause of the indexing wheel, when the packet is ejected from the pocket by a radial push rod and directed into a runout channel, whereupon the projecting portion of the strip is promptly folded down and held in place against the uppermost face of the packet by the top surface of this same channel.
Besides being subject to the limitations on speed imposed by intermittent operation, such a device is beset by other drawbacks.
First, the fact that the runout channel is designed to fold and restrain the projecting portion of the strip dictates that it be substantially equal in height to the depth of the packet; thus, the faces of the packet can be defaced by the channel walls. Moreover, friction between the top of the channel and the projecting portion of the strip can result in the strip itself slipping out of its correct position, or even becoming detached from the packet altogether.